Showing papers by "John Radcliffe Hospital published in 2018"

The UK Biobank resource with deep phenotyping and genomic data

Abstract: The UK Biobank project is a prospective cohort study with deep genetic and phenotypic data collected on approximately 500,000 individuals from across the United Kingdom, aged between 40 and 69 at recruitment. The open resource is unique in its size and scope. A rich variety of phenotypic and health-related information is available on each participant, including biological measurements, lifestyle indicators, biomarkers in blood and urine, and imaging of the body and brain. Follow-up information is provided by linking health and medical records. Genome-wide genotype data have been collected on all participants, providing many opportunities for the discovery of new genetic associations and the genetic bases of complex traits. Here we describe the centralized analysis of the genetic data, including genotype quality, properties of population structure and relatedness of the genetic data, and efficient phasing and genotype imputation that increases the number of testable variants to around 96 million. Classical allelic variation at 11 human leukocyte antigen genes was imputed, resulting in the recovery of signals with known associations between human leukocyte antigen alleles and many diseases.

Sickle cell disease

Abstract: Sickle cell disease (SCD) is a group of inherited disorders caused by mutations in HBB, which encodes haemoglobin subunit β. The incidence is estimated to be between 300,000 and 400,000 neonates globally each year, the majority in sub-Saharan Africa. Haemoglobin molecules that include mutant sickle β-globin subunits can polymerize; erythrocytes that contain mostly haemoglobin polymers assume a sickled form and are prone to haemolysis. Other pathophysiological mechanisms that contribute to the SCD phenotype are vaso-occlusion and activation of the immune system. SCD is characterized by a remarkable phenotypic complexity. Common acute complications are acute pain events, acute chest syndrome and stroke; chronic complications (including chronic kidney disease) can damage all organs. Hydroxycarbamide, blood transfusions and haematopoietic stem cell transplantation can reduce the severity of the disease. Early diagnosis is crucial to improve survival, and universal newborn screening programmes have been implemented in some countries but are challenging in low-income, high-burden settings.

MOG encephalomyelitis: International recommendations on diagnosis and antibody testing

Abstract: Over the past few years, new-generation cell-based assays have demonstrated a robust association of autoantibodies to full-length human myelin oligodendrocyte glycoprotein (MOG-IgG) with (mostly recurrent) optic neuritis, myelitis and brainstem encephalitis, as well as with acute disseminated encephalomyelitis (ADEM)-like presentations. Most experts now consider MOG-IgG-associated encephalomyelitis (MOG-EM) a disease entity in its own right, immunopathogenetically distinct from both classic multiple sclerosis (MS) and aquaporin-4 (AQP4)-IgG-positive neuromyelitis optica spectrum disorders (NMOSD). Owing to a substantial overlap in clinicoradiological presentation, MOG-EM was often unwittingly misdiagnosed as MS in the past. Accordingly, increasing numbers of patients with suspected or established MS are currently being tested for MOG-IgG. However, screening of large unselected cohorts for rare biomarkers can significantly reduce the positive predictive value of a test. To lessen the hazard of overdiagnosing MOG-EM, which may lead to inappropriate treatment, more selective criteria for MOG-IgG testing are urgently needed. In this paper, we propose indications for MOG-IgG testing based on expert consensus. In addition, we give a list of conditions atypical for MOG-EM (“red flags”) that should prompt physicians to challenge a positive MOG-IgG test result. Finally, we provide recommendations regarding assay methodology, specimen sampling and data interpretation.

Neuroscience of apathy and anhedonia: a transdiagnostic approach

Abstract: Apathy and anhedonia are common syndromes of motivation that are associated with a wide range of brain disorders and have no established therapies. Research using animal models suggests that a useful framework for understanding motivated behaviour lies in effort-based decision making for reward. The neurobiological mechanisms underpinning such decisions have now begun to be determined in individuals with apathy or anhedonia, providing an important foundation for developing new treatments. The findings suggest that there might be some shared mechanisms between both syndromes. A transdiagnostic approach that cuts across traditional disease boundaries provides a potentially useful means for understanding these conditions.

Disease Course and Treatment Responses in Children With Relapsing Myelin Oligodendrocyte Glycoprotein Antibody–Associated Disease

Abstract: Importance Myelin oligodendrocyte glycoprotein antibodies (MOG-Abs) are consistently identified in a range of demyelinating disorders in adults and children. Current therapeutic strategies are largely center specific, and no treatments have been formally evaluated. Objective To examine the clinical phenotypes, treatment responses, and outcomes of children with relapsing MOG-Ab–associated disease. Design, Setting, and Participants This study prospectively collected demographic, clinical, and radiologic data from 102 patients from 8 countries of the EU Paediatric Demyelinating Disease Consortium from January 1, 2014, through December 31, 2016. Patients were treated according to local protocols. Main Outcomes and Measures Annualized relapse rates (ARRs) and Expanded Disability Status Scale (EDSS) scores before and during treatment with disease-modifying drugs (DMDs). Results A total of 102 children were identified (median [range] age, 7.0 [1.5-7.9] years; male to female ratio, 1.0:1.8; white to other race/ethnicity ratio, 3.6:1.0). Original diagnoses were neuromyelitis optica spectrum disorder (44 patients [43.1%]), acute disseminated encephalomyelitis followed by optic neuritis (20 [19.6%]), multiphasic disseminated encephalomyelitis (20 [19.6%]), and relapsing optic neuritis (18 [17.6%]). In all, 464 demyelinating events were reported. Treated patients had more relapses (median, 3.0; range, 1.0-17.0) than untreated patients (median, 1.0; range 1.0-7.0) (P = .009) and higher EDSS scores (median, 1.5; interquartile range, 0-2.5) than untreated patients (median, 1.0; interquartile range, 0-1.5) (P Conclusions and Relevance Although commonly used to treat patients with multiple sclerosis, DMDs were not associated with clinical improvement in children with MOG-Ab–associated disease, whereas azathioprine, mycophenolate mofetil, rituximab, and particularly intravenous immunoglobulins were associated with a reduction in relapse frequency. A correct diagnosis of relapsing MOG-Ab–associated disorders is therefore important to optimize immune treatment.

Anxiety, Depression and Post Traumatic Stress Disorder after critical illness: a UK-wide prospective cohort study.

Abstract: Survivors of intensive care are known to be at increased risk of developing longer-term psychopathology issues. We present a large UK multicentre study assessing the anxiety, depression and post-traumatic stress disorder (PTSD) caseness in the first year following discharge from an intensive care unit (ICU). Design: prospective multicentre follow-up study of survivors of ICU in the UK. Setting: patients from 26 ICUs in the UK. Inclusion criteria: patients who had received at least 24 h of level 3 ICU care and were 16 years of age or older. Interventions: postal follow up: Hospital Anxiety and Depression Score (HADS) and the Post-Traumatic Stress Disorder (PTSD) Check List-Civilian (PCL-C) at 3 and 12 months following discharge from ICU. Main outcome measure: caseness of anxiety, depression and PTSD, 2-year survival. In total, 21,633 patients admitted to ICU were included in the study. Postal questionnaires were sent to 13,155 survivors; of these 38% (4943/13155) responded and 55% (2731/4943) of respondents passed thresholds for one or more condition at 3 or 12 months following discharge. Caseness prevalence was 46%, 40% and 22% for anxiety, depression and PTSD respectively; 18% (870/4943 patients) met the caseness threshold for all three psychological conditions. Patients with symptoms of depression were 47% more likely to die during the first 2 years after discharge from ICU than those without (HR 1.47, CI 1.19–1.80). Over half of those who respond to postal questionnaire following treatment on ICU in the UK reported significant symptoms of anxiety, depression or PTSD. When symptoms of one psychological disorder are present, there is a 65% chance they will co-occur with symptoms of one of the other two disorders. Depression following critical illness is associated with an increased mortality risk in the first 2 years following discharge from ICU. ISRCTN Registry, ISRCTN69112866 . Registered on 2 May 2006.

Dementia And Physical Activity (DAPA) trial of moderate to high intensity exercise training for people with dementia: randomised controlled trial

Abstract: Objective To estimate the effect of a moderate to high intensity aerobic and strength exercise training programme on cognitive impairment and other outcomes in people with mild to moderate dementia. Design Multicentre, pragmatic, investigator masked, randomised controlled trial. Setting National Health Service primary care, community and memory services, dementia research registers, and voluntary sector providers in 15 English regions. Participants 494 people with dementia: 329 were assigned to an aerobic and strength exercise programme and 165 were assigned to usual care. Random allocation was 2:1 in favour of the exercise arm. Interventions Usual care plus four months of supervised exercise and support for ongoing physical activity, or usual care only. Interventions were delivered in community gym facilities and NHS premises. Main outcome measures The primary outcome was score on the Alzheimer’s disease assessment scale-cognitive subscale (ADAS-cog) at 12 months. Secondary outcomes included activities of daily living, neuropsychiatric symptoms, health related quality of life, and carer quality of life and burden. Physical fitness (including the six minute walk test) was measured in the exercise arm during the intervention. Results The average age of participants was 77 (SD 7.9) years and 301/494 (61%) were men. By 12 months the mean ADAS-cog score had increased to 25.2 (SD 12.3) in the exercise arm and 23.8 (SD 10.4) in the usual care arm (adjusted between group difference −1.4, 95% confidence interval −2.6 to −0.2, P=0.03). This indicates greater cognitive impairment in the exercise group, although the average difference is small and clinical relevance uncertain. No differences were found in secondary outcomes or preplanned subgroup analyses by dementia type (Alzheimer’s disease or other), severity of cognitive impairment, sex, and mobility. Compliance with exercise was good. Over 65% of participants (214/329) attended more than three quarters of scheduled sessions. Six minute walking distance improved over six weeks (mean change 18.1 m, 95% confidence interval 11.6 m to 24.6 m). Conclusion A moderate to high intensity aerobic and strength exercise training programme does not slow cognitive impairment in people with mild to moderate dementia. The exercise training programme improved physical fitness, but there were no noticeable improvements in other clinical outcomes. Trial registration Current Controlled Trials ISRCTN10416500.

GWAS identifies 14 loci for device-measured physical activity and sleep duration.

Abstract: Physical activity and sleep duration are established risk factors for many diseases, but their aetiology is poorly understood, partly due to relying on self-reported evidence. Here we report a genome-wide association study (GWAS) of device-measured physical activity and sleep duration in 91,105 UK Biobank participants, finding 14 significant loci (7 novel). These loci account for 0.06% of activity and 0.39% of sleep duration variation. Genome-wide estimates of ~ 15% phenotypic variation indicate high polygenicity. Heritability is higher in women than men for overall activity (23 vs. 20%, p = 1.5 × 10−4) and sedentary behaviours (18 vs. 15%, p = 9.7 × 10−4). Heritability partitioning, enrichment and pathway analyses indicate the central nervous system plays a role in activity behaviours. Two-sample Mendelian randomisation suggests that increased activity might causally lower diastolic blood pressure (beta mmHg/SD: −0.91, SE = 0.18, p = 8.2 × 10−7), and odds of hypertension (Odds ratio/SD: 0.84, SE = 0.03, p = 4.9 × 10−8). Our results advocate the value of physical activity for reducing blood pressure. Studying the genetic underpinnings of physical activity and sleep duration can be confounded by self-reporting. Here, Doherty et al. use data from 91,105 UK Biobank participants, whose activity had been monitored for a week by a wearable device, for genome-wide association analysis and identify 14 loci.

Mechanistic models versus machine learning, a fight worth fighting for the biological community?

Abstract: Ninety per cent of the world's data have been generated in the last 5 years (Machine learning: the power and promise of computers that learn by example Report no. DES4702. Issued April 2017. Royal Society). A small fraction of these data is collected with the aim of validating specific hypotheses. These studies are led by the development of mechanistic models focused on the causality of input-output relationships. However, the vast majority is aimed at supporting statistical or correlation studies that bypass the need for causality and focus exclusively on prediction. Along these lines, there has been a vast increase in the use of machine learning models, in particular in the biomedical and clinical sciences, to try and keep pace with the rate of data generation. Recent successes now beg the question of whether mechanistic models are still relevant in this area. Said otherwise, why should we try to understand the mechanisms of disease progression when we can use machine learning tools to directly predict disease outcome?

The distribution of bacterial doubling times in the wild.

Abstract: Generation time varies widely across organisms and is an important factor in the life cycle, life history and evolution of organisms. Although the doubling time (DT) has been estimated for many bacteria in the laboratory, it is nearly impossible to directly measure it in the natural environment. However, an estimate can be obtained by measuring the rate at which bacteria accumulate mutations per year in the wild and the rate at which they mutate per generation in the laboratory. If we assume the mutation rate per generation is the same in the wild and in the laboratory, and that all mutations in the wild are neutral, an assumption that we show is not very important, then an estimate of the DT can be obtained by dividing the latter by the former. We estimate the DT for five species of bacteria for which we have both an accumulation and a mutation rate estimate. We also infer the distribution of DTs across all bacteria from the distribution of the accumulation and mutation rates. Both analyses suggest that DTs for bacteria in the wild are substantially greater than those in the laboratory, that they vary by orders of magnitude between different species of bacteria and that a substantial fraction of bacteria double very slowly in the wild.

Percutaneous coronary intervention for the left main stem and other bifurcation lesions: 12th consensus document from the European Bifurcation Club.

Abstract: The European Bifurcation Club (EBC) was initiated in 2004 to support a continuous overview of the field of coronary artery bifurcation interventions and aims to facilitate a scientific discussion and an exchange of ideas on the management of bifurcation disease. The EBC hosts an annual, two-day compact meeting, dedicated to bifurcations, which brings together physicians, pathologists, engineers, biologists, physicists, mathematicians, epidemiologists and statisticians for detailed discussions. Every meeting is finalised with a consensus statement that reflects the unique opportunity of combining the opinion of interventional cardiologists with the opinion of a large variety of other scientists on bifurcation management. A series of consensus sessions dedicated to specific topics, to strengthen the consensus debates and focus the discussions, was introduced at this year's meeting. The sessions comprise an intensive overview of the present literature, a pro and con debate and a voting system, to guide the consensus-building process. The present document represents the summary of the up-to-date EBC consensus and recommendations from the 12th annual EBC meeting in 2016 in Rotterdam.

Seizures and Encephalitis in Myelin Oligodendrocyte Glycoprotein IgG Disease vs Aquaporin 4 IgG Disease

Abstract: Importance Antibodies to myelin oligodendrocyte glycoprotein IgG (MOG-IgG) are increasingly detected in patients with non–multiple sclerosis–related demyelination, some of whom manifest a neuromyelitis optica (NMO) phenotype. Cortical involvement, encephalopathy, and seizures are rare in aquaporin 4 antibody (AQP4-IgG)–related NMO in the white European population. However, the authors encountered several patients with seizures associated with MOG-IgG disease. Objective To compare incidence of seizures and encephalitis-like presentation, or both between AQP4-IgG–positive and MOG-IgG–positive patients. Design, Setting, and Participants Retrospective case series of all patients who were seropositive for MOG-IgG (n = 34) and the last 100 patients with AQP4-IgG disease (NMO spectrum disorder) seen in the NMO service between January 2013 and December 2016, and analysis was completed January 4, 2017. All patients were seen in a tertiary neurological center, The Walton Centre NHS Foundation Trust in Liverpool, England. Main Outcomes and Measures The difference in seizure frequency between the AQP4-IgG–positive and MOG-IgG–positive patient groups was determined. Results Thirty-four patients with MOG-IgG disease (20 female) with a median age at analysis of 30.5 years (interquartile range [IQR], 15-69 years), and 100 AQP4-IgG–positive patients (86 female) with a median age at analysis of 54 years (IQR, 12-91 years) were studied. Most patients were of white race. Five of the 34 patients with MOG-IgG (14.7%) had seizures compared with 1 patient with AQP4-IgG (2-sided P Conclusions and Relevance Patients with MOG-IgG–associated disease were more likely to have seizures and encephalitis-like presentation than patients with AQP4-IgG–associated disease.

Complications of endovascular treatment for acute ischemic stroke: Prevention and management:

Abstract: Endovascular mechanical thrombectomy (MT) for the treatment of acute stroke due to large vessel occlusion has evolved significantly with the publication of multiple positive thrombectomy trials. MT is now a recommended treatment for acute ischemic stroke. Mechanical thrombectomy is associated with a number of intra-procedural or post-operative complications, which need to be minimized and effectively managed to maximize the benefits of thrombectomy. Procedural complications include: access-site problems (vessel/nerve injury, access-site hematoma and groin infection); device-related complications (vasospasm, arterial perforation and dissection, device detachment/misplacement); symptomatic intracerebral hemorrhage; subarachnoid hemorrhage; embolization to new or target vessel territory. Other complications include: anesthetic/contrast-related, post-operative hemorrhage, extra-cranial hemorrhage and pseudoaneurysm. Some complications are life-threatening and many lead to increased length of stay in intensive care and stroke units. Complications increase costs and delay the commencement of rehabilitation. Some may be preventable; the impact of others can be minimized with early detection and appropriate management. Both neurointerventionists and stroke specialists need to be aware of the risk factors, strategies for prevention, and management of these complications. With the increasing use of mechanical thrombectomy for the treatment of acute ischemic stroke, incidence and outcome of complications will need to be carefully monitored by stroke teams. In this narrative review, we examine the frequency of complications of MT in the treatment of acute ischemic stroke with an emphasis on periprocedural complications. Overall, from recent randomized controlled trials, the risk of complications with sequelae for patient from mechanical thrombectomy is ∼15%. We discuss the management of complications and identify areas with limited evidence, which need further research. Search strategy and selection criteria Relevant evidence was found by searches of Medline and Cochrane Library, reference list, cross-referencing and main journal content pages. Search terms included "brain ischemia", "acute ischemic stroke", "cerebral infarction" AND "mechanical thrombectomy", "endovascular therapy", "endovascular treatment", "endovascular embolectomy", "intra-arterial" AND "randomized controlled trial", "non-randomised trials", "observational studies" AND "complications", "procedural complications", "peri-procedural complications", "device-related complications", "management", "treatment", "outcome". The search included only human studies, and was limited to studies published in English between January 2014 and November 2016. The final reference list was selected on the basis of relevance to the topics covered in the Review. Guidelines for management of acute ischaemic stroke by the American Heart Association, the European Stroke Organisation, multi-disciplinary guidelines and the National Institute for Health and Care Excellence (NICE) were also reviewed.

A public antibody lineage that potently inhibits malaria infection through dual binding to the circumsporozoite protein

Abstract: Immunization with attenuated Plasmodium falciparum sporozoites (PfSPZs) has been shown to be protective against malaria, but the features of the antibody response induced by this treatment remain unclear. To investigate this response in detail, we isolated IgM and IgG monoclonal antibodies from Tanzanian volunteers who were immunized with repeated injection of Sanaria PfSPZ Vaccine and who were found to be protected from controlled human malaria infection with infectious homologous PfSPZs. All isolated IgG monoclonal antibodies bound to P. falciparum circumsporozoite protein (PfCSP) and recognized distinct epitopes in its N terminus, NANP-repeat region, and C terminus. Strikingly, the most effective antibodies, as determined in a humanized mouse model, bound not only to the repeat region, but also to a minimal peptide at the PfCSP N-terminal junction that is not in the RTS,S vaccine. These dual-specific antibodies were isolated from different donors and were encoded by VH3-30 or VH3-33 alleles that encode tryptophan or arginine at position 52. Using structural and mutational data, we describe the elements required for germline recognition and affinity maturation. Our study provides potent neutralizing antibodies and relevant information for lineage-targeted vaccine design and immunization strategies.

The cardiac lymphatic system stimulates resolution of inflammation following myocardial infarction

Abstract: Myocardial infarction (MI) arising from obstruction of the coronary circulation engenders massive cardiomyocyte loss and replacement by non-contractile scar tissue, leading to pathological remodeling, dysfunction, and ultimately heart failure. This is presently a global health problem for which there is no effective cure. Following MI, the innate immune system directs the phagocytosis of dead cell debris in an effort to stimulate cell repopulation and tissue renewal. In the mammalian adult heart, however, the persistent influx of immune cells, coupled with the lack of an inherent regenerative capacity, results in cardiac fibrosis. Here, we reveal that stimulation of cardiac lymphangiogenesis with VEGF-C improves clearance of the acute inflammatory response after MI by trafficking immune cells to draining mediastinal lymph nodes (MLNs) in a process dependent on lymphatic vessel endothelial hyaluronan receptor 1 (LYVE-1). Deletion of Lyve1 in mice, preventing docking and transit of leukocytes through the lymphatic endothelium, results in exacerbation of chronic inflammation and long-term deterioration of cardiac function. Our findings support targeting of the lymphatic/immune cell axis as a therapeutic paradigm to promote immune modulation and heart repair.

Advances in therapy for spinal muscular atrophy: promises and challenges.

Abstract: Spinal muscular atrophy (SMA) is a devastating motor neuron disease that predominantly affects children and represents the most common cause of hereditary infant mortality. The condition results from deleterious variants in SMN1, which lead to depletion of the survival motor neuron protein (SMN). Now, 20 years after the discovery of this genetic defect, a major milestone in SMA and motor neuron disease research has been reached with the approval of the first disease-modifying therapy for SMA by US and European authorities - the antisense oligonucleotide nusinersen. At the same time, promising data from early-stage clinical trials of SMN1 gene therapy have indicated that additional therapeutic options are likely to emerge for patients with SMA in the near future. However, the approval of nusinersen has generated a number of immediate and substantial medical, ethical and financial implications that have the potential to resonate beyond the specific treatment of SMA. Here, we provide an overview of the rapidly evolving therapeutic landscape for SMA, highlighting current achievements and future opportunities. We also discuss how these developments are providing important lessons for the emerging second generation of combinatorial ('SMN-plus') therapies that are likely to be required to generate robust treatments that are effective across a patient's lifespan.

Cognition and dementia in older patients with epilepsy.

Abstract: With advances in healthcare and an ageing population, the number of older adults with epilepsy is set to rise substantially across the world. In developed countries the highest incidence of epilepsy is already in people over 65 and, as life expectancy increases, individuals who developed epilepsy at a young age are also living longer. Recent findings show that older persons with epilepsy are more likely to suffer from cognitive dysfunction and that there might be an important bidirectional relationship between epilepsy and dementia. Thus some people with epilepsy may be at a higher risk of developing dementia, while individuals with some forms of dementia, particularly Alzheimer's disease and vascular dementia, are at significantly higher risk of developing epilepsy. Consistent with this emerging view, epidemiological findings reveal that people with epilepsy and individuals with Alzheimer's disease share common risk factors. Recent studies in Alzheimer's disease and late-onset epilepsy also suggest common pathological links mediated by underlying vascular changes and/or tau pathology. Meanwhile electrophysiological and neuroimaging investigations in epilepsy, Alzheimer's disease, and vascular dementia have focused interest on network level dysfunction, which might be important in mediating cognitive dysfunction across all three of these conditions. In this review we consider whether seizures promote dementia, whether dementia causes seizures, or if common underlying pathophysiological mechanisms cause both. We examine the evidence that cognitive impairment is associated with epilepsy in older people (aged over 65) and the prognosis for patients with epilepsy developing dementia, with a specific emphasis on common mechanisms that might underlie the cognitive deficits observed in epilepsy and Alzheimer's disease. Our analyses suggest that there is considerable intersection between epilepsy, Alzheimer's disease and cerebrovascular disease raising the possibility that better understanding of shared mechanisms in these conditions might help to ameliorate not just seizures, but also epileptogenesis and cognitive dysfunction.

Pedunculopontine nucleus deep brain stimulation in Parkinson's disease: A clinical review

Abstract: Pedunculopontine nucleus region deep brain stimulation (DBS) is a promising but experimental therapy for axial motor deficits in Parkinson's disease (PD), particularly gait freezing and falls. Here, we summarise the clinical application and outcomes reported during the past 10 years. The published dataset is limited, comprising fewer than 100 cases. Furthermore, there is great variability in clinical methodology between and within surgical centers. The most common indication has been severe medication refractory gait freezing (often associated with postural instability). Some patients received lone pedunculopontine nucleus DBS (unilateral or bilateral) and some received costimulation of the subthalamic nucleus or internal pallidum. Both rostral and caudal pedunculopontine nucleus subregions have been targeted. However, the spread of stimulation and variance in targeting means that neighboring brain stem regions may be implicated in any response. Low stimulation frequencies are typically employed (20-80 Hertz). The fluctuating nature of gait freezing can confound programming and outcome assessments. Although firm conclusions cannot be drawn on therapeutic efficacy, the literature suggests that medication refractory gait freezing and falls can improve. The impact on postural instability is unclear. Most groups report a lack of benefit on gait or limb akinesia or dopaminergic medication requirements. The key question is whether pedunculopontine nucleus DBS can improve quality of life in PD. So far, the evidence supporting such an effect is minimal. Development of pedunculopontine nucleus DBS to become a reliable, established therapy would likely require a collaborative effort between experienced centres to clarify biomarkers predictive of response and the optimal clinical methodology. © 2017 International Parkinson and Movement Disorder Society.